This is the beginning of a relatively large concepts/type-traits refactor that is going to come in over the next while. First is factoring out convertible_to so it looks/works more like the standard library version so I can start converting detector into a more user-friendly version we can actually expose.  This is a bug for GEOSX and others, and should also make our type_traits more robust once it's all in.

With the is_convertible changes, this is the basis for the whole
refactor setup.  Concepts will all be defined against the new detector,
as will type traits, using the new idiom through the macro so if we need
to do this again it wont have to touch them all.

tests integrated, and some concepts ported, more to go

concepts are working again, and actually have tests in detect.cpp, there
are new macros for defining detectors, requirements (helper for
detectors), concepts, and all-in-one doing a concept and associated
traits.  It's possible there are breaking changes in here if anyone
external is relying on the concepts, but since many of them were broken
I'm hoping this will be a net benefit.

Remove unnecessary stl headers, factor out their usage, also use
builtins for typelist lookups when available.

In C++17 mode use built-in fold expressions, in 14 use a simpler type.
When in 14 mode this buys up to 30% improvement, in 17 mode it's almost
four *times* faster to instantiate tuples now.  Should help with RAJA
compile times where 17 is available.

Turn tuple_storage into an aggregate when possible, turns out this is
not possible on nvcc right now, but elsewhere it's a nice little 5-20%
bump.